import re


def main():
    email = input("请输入邮箱地址:")
    ret = re.match(r"^[a-zA-Z0-9]{4,20}@163\.com$", email)
    if ret:
        print("邮箱 %s 符合要求" % ret.group())
    else:
        print("邮箱 %s 不符合要求" % email)

    re.sub()
if __name__ == '__main__':
    main()
